My spirit, my mind, my soul, whatever these concepts mean for me or anyone else. It's not outside of myself. That experience is truly mine. By extension, my thoughts are mine. Assuming you test your thoughts always against the influence of the crowd and the influence of others have on your thoughts. But that is yours and yours alone.
I can't think of much to add beyond what I've said this morning except for knowing it intellectually is one thing, putting it into practice is another.
Title prompts are taken from The Daily Stoic Journal by Ryan Holiday and Stephen Hanselman.